Ecological exeriments on Foraminiferida

Abstract

Fifteen experiments on the foraminiferid Elphidium crispum (L.) are described. They deal with feeding, movement, the substratum, and salinity, and their bearing on ecology.The daily production of feeding cysts was used as a measure of the metabolic rate and healthiness of the foraminiferids. Phaeodactylum tricornutum, both living and dead, was used as food; a distinct preference was shown for living food. However, kaolin and graphite having a similar size to the Phaeodactylum were also accepted as food. It is suggested that E. crispum selects its food on the basis of size. The colour of the protoplasm is shown to be closely related to the pigments of the foodMovement in the horizontal plane is normally random. However, this species prefers a clean, hard substratum to one of clay; once a specimen has escaped from a clay substratum, it is loathe to return to it and therefore movement in this instance must be directed and not random.Movement in the horizontal plane is normally random. However, this species prefers a clean, hard substratum to one of clay; once a specimen has escaped from a clay substratum, it is loathe to return to it and therefore movement in this instance must be directed and not random.The rate of feeding is shown to be closely related to the salinity of the water, the feeding rate decreasing with the salinity. The amount of calcium present in sea water or in subsaline waters does not appear to affect the rate of feeding. However, lowered temperatures help E. crispum to survive for longer periods in subsaline water. At temperatures of 8° and 16° C , cultures survived subsaline water of 20%0 salinity for 38 days, but at a salinity of i5%03 only the culture kept at 8 C survived (for 15 days).